Conveyors for vehicles such as automobiles or the like are utilized frequently in drive-through car washes as well as other applications in which it is desirable to slowly advance a vehicle across a horizontal floor surface. One of the most common type of conveyors utilized is the "in the floor" type such as that shown in U.S. Pat. No. 4,576,098, Belanger et al. A guided track extends along the floor surface and the conveyor mechanism is oriented in an elongated trench below the floor immediately under the guided track. On demand, a dolly will rise out of an opening at the entrance end of the conveyor for engaging the tire of a vehicle which has been properly staged in the conveyor. The dolly will gradually advance the vehicle along the conveyor until the vehicle exits and the dolly drops below floor level to begin its said return flight. It should be noted that dollies have two alternative paths on the drive flight, one path below floor level where the dolly is totally out of the way and an alternative path above floor level within the guided track for engaging the vehicle tire. Dollies can be spaced sufficiently close together so as to enable a series of automobiles being translated along the conveyor to be positioned relatively close apart to achieve maximum vehicle through put.
Below the floor conveyors are widely used in North America and function quite satisfactorily, however, they are expensive to install due to the required concrete work necessary to embed the conveyor below the floor surface. The necessity for concrete work not only adds expense and length of construction and installation time, it becomes difficult and expensive to return the building to its original state if the building is to be subsequently used for a different purpose.
In order to minimize some of the problems associated with below the floor conveyors there have been many efforts over the years to build a commercially feasible above the floor conveyor for use in car washes or the like. Examples of prior art above the floor conveyors are illustrated in the following patents: U.S. Pat. No. 3,196,806, U.S. Pat. No. 3,677,190, U.S. Pat. No. 3,719,151, U.S. Pat. No. 3,744,433, U.S. Pat. No. 3,815,512, U.S. Pat. No. 3,861,324. Most of the preceding patents are not truly above the floor conveyors since a substantial part of the conveyor drive mechanism or the dolly activation mechanism is oriented below floor level.
Typical prior art floor mounted conveyors merely minimize the amount of concrete work necessary, and cannot be installed upon a flat horizontal concrete surface unless a platform is used at least locally, to space the conveyor to floor. An exception to this general statement is U.S. Pat. No. 3,861,324 which has spaced the conveyor sufficiently above the floor as illustrated in FIG. 2, so as to enable the drive motor chain to pass beneath the platforms on which the vehicle tires ride. U.S. Pat. No. 3,744,433 also appears to be a truly above the floor conveyor of the "on demand" type. It should be noted that the "on demand" feature is achieved by removably connecting the dollies to the conveyor drive chain so that the dollies do not need to be transported along the drive flight of the conveyor in an inactive position. The mechanism required to remove and reinstall the dolly is relatively complicated adding to the cost and the complexity of the conveyor.